This invention relates to a reproducing stylus for a record and, in particular, to an improved shape thereof including a method for making the shape.
The shape of reproducing stylus tips for records developed from a round stylus to an elliptical stylus in order to reduce tracing distortion, which is required for stereophonic reproduction. Subsequently, a line contact stylus was developed in order to improve the high frequency responses required for 4-channel reproduction. FIG. 1 shows front views, a round stylus (a), an elliptical stylus (b), and a line contact stylus (c). Cross-sectional views of the contact areas of these respective styli with the record sound groove 2 are shown at (d), (e), and (f). The elliptical stylus (b) was formed in order to eliminate the pinch effect and tracing distortion occurring with round stylus (a) and to reduce the radius r.sub.1 of the stylus tip curvature at the contact area with the phonograph record. The line contact stylus (c) was formed by further reducing the radius r.sub.2 of the stylus tip curvature by special grinding to radius r.sub.3 for line contact with the record sound groove 2, which expanded the reproduction frequency band as well as reduced friction of the reproducing stylus to a minimum. Various shapes and manufacturing methods have since been proposed. However, when the frequency responses of a pick-up cartridge attributable only to the radius of stylus tip curvature are considered, there are differences in the treble reproduction ability and responses between the outer circumference 3 and the inner circumference 4 of the phonograph record as seen in the case of a round stylus (a), an elliptical stylus (b), and a line contact stylus (c) shown in FIG. 2 respectively. This is directly related to the tracing distortion attributable to the radius of stylus tip curvature, and it has been considered very difficult to manufacture a stylus tip shape to obtain a radius of stylus tip curvature smaller than that of the currently available, most superior line contact stylus.